Method of sealing organo electro-luminescent display
A top-emission organic electro-luminescent display (OLED) has a substrate with at least a anode layer, an organic fluorescent film, at least a cathode layer, a barrier layer and a protection layer. A transparent sealing structure is glued to the top of the substrate. Wherein, the transparent sealing structure has an adhesion layer glued to the protection layer, a plurality of organic resin layers formed on the adhesion layer, a plurality of inorganic barrier layers disposed between the organic resin layers, a flexible polymer film formed on the organic resin layer, and a hard coat formed on the flexible polymer film.
This application is a divisional of application Ser. No. 09/995,447, filed Nov. 27, 2001, pending, which application(s) are incorporated herein by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to an organic electro-luminescent display (OLED) and a method of forming the same and, more particularly, to a top-emission OLED and a method of sealing the same.
2. Description of the Related Art
In the new generation of flat panel techniques, organic electro-luminescent display (OLED) has advantages of self-luminescence, wide-view angle, thin profile, lightweight, low driving voltage and simple process. In OLEDs with a laminated structure, organic compounds such as dyes, polymers, or other luminescent materials serve as an organic luminescent layer and are disposed between cathode and anode. In accordance with the driving mode, OLED is classified into passive matrix and active matrix types. Alternatively, in accordance with the luminescent path, OLED is classified into a bottom-emission OLED and a top-emission OLED. Conventionally, both of the passive and active matrix types are fabricated as the bottom-emission OLED in which glass material is used to form the luminescent faceplate and transparent conductive material is used to form the anode layer. Thus, when electrons and holes are combined as excitons in the organic luminescent layer, light radiates from the transparent faceplate. However, since the luminescent regions of the R, G and B are different within each pixel area, TFT structures in array have different sizes and thus reduce the aperture ratio of the bottom-emission OLED.
In order to increase the aperture ratio, a top-emission OLED is developed in which the cathode layer is transparent materials and a transparent faceplate is sealed on the top of the OLED.
However, as the duration of use increases, the probability of moisture and oxygen permeating the OLED also increases, causing detachment between the organic luminescent layer 14 and the cathode electrode 16, cracking of the organic materials, and oxidation of the electrodes. As a result, a so-called “dark spot”, to which electricity is not supplied, is generated, decreasing luminescence and luminescent uniformity. Accordingly, in conventionally sealing the top of the top-emission OLED, one method uses a glass plate to isolate moisture/oxygen from the outer environment, but the glass plate with large volume and weight does not fit the requirements of the OLED. The other method coats a UV-curing resin on the top of the top-emission OLED to provide a transparent result, but the resin with outgassing phenomenon and poor resistance to moisture cannot assure the luminescent property of the OLED. Thus, a novel sealing structure of the top-emission OLED solving the aforementioned problems is called for.
SUMMARY OF THE INVENTIONThe present invention provides a top-emission OLED and a method of sealing the same to increase aperture ratio and resistance to moisture.
The top-emission organic electro-luminescent display (OLED) has a substrate with at least a lengthwise-extending anode layer, an organic fluorescent film, at least a transversely-extending cathode layer, a barrier layer and a protection layer. A transparent sealing structure is glued to the top of the substrate. The transparent sealing structure has an adhesion layer glued to the protection layer, a plurality of organic resin layers formed on the adhesion layer, a plurality of inorganic barrier layers disposed between the organic resin layers, a flexible polymer film formed on the organic resin layer, and a hard coat formed on the flexible polymer film.
Accordingly, it is a principle object of the invention to provide the inorganic barrier layer to achieve a good resistance to moisture/oxygen.
It is another object of the invention to provide the organic resin layer to decrease the internal stress generated by the organic barrier layer and assure the planarization of the sealing structure.
Yet another object of the invention is to provide the hard coat to obstruct the permeation/pollution of moisture, oxygen and impurities.
It is a further object of the invention to provide the sealing structure to achieve good planarization, excellent resistance to moisture and sufficient transparency.
Still another object of the invention is to provide the sealing structure to promote the luminescent property and lifetime of the top-emission OLED.
Another object of the invention is to provide the sealing structure to achieve commercial requirements of the top-emission OLED, such as light weight and thin type.
These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.
Similar reference characters denote corresponding features consistently throughout the attached drawings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTSThe present invention provides a sealing structure of a top-emission OLED and a method of sealing the same, in which the top-emission OLED is applied to a passive matrix type or an active matrix type. In sealing the top-emission OLED, the sealing structure formed as laminated film is glued to the top of the top-emission OLED. This method is simple and the sealing structure provides a favorable aperture ratio and excellent resistance to moisture/oxygen.
The anode layer 22 and cathode layer 28 are formed using conductive materials with low resistance and low work function, wherein the work function is the required energy (eV) for driving charges. Also, since the cathode layer 28 needs to be transparent, transparent conductive materials are preferred for the use of the cathode layer 28. The transparent barrier layer 30 uses inorganic materials, such as SiO, SiOx, SiO2, and Si3N4, those are formed by plasma enhanced chemical vapor deposition (PECVD). The transparent protection layer 32 uses organic materials, such as resin by spin-on coating, resulting in a planarized surface.
In sealing the top-emission OLED, when the barrier layer 30 and the protection layer 32 are completed on the substrate 20, the adhesion layer 36 is coated at the bottom of the sealing structure 34 or coated on the top of the substrate 20. Then, using a roll-press manner, the sealing structure 34 is glued to the top of the top-emission OLED. This sealing method is simple to reduce process costs and increase throughput of the top-emission OLED.
It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.
Claims
1. A method of sealing a top-emission organic electro-luminescent display (OLED), comprising steps of:
- providing a substrate which has at least an anode layer, an organic fluorescent film, at least a cathode layer, a barrier layer and a protection layer;
- adhering a transparent sealing structure which has a plurality of organic resin layers formed on a first side of a flexible polymer film, a plurality of inorganic barrier layers disposed between the organic resin layers;
- providing a hard coat formed on a second side of the flexible polymer film; and
- adhering the transparent sealing structure to the protection layer of the substrate by a first transparent adhesion layer after forming the transparent sealing structure.
2. The method according to claim 1, wherein the first transparent adhesion layer is formed at the organic resin layer of the transparent sealing structure.
3. The method according to claim 1, wherein the first transparent adhesion layer is formed on the protection layer of the substrate.
4. The method according to claim 1, wherein the transparent sealing structure is adhered to the protection layer of the substrate by a roll-press manner.
5. The method according to claim 1, wherein the transparent sealing structure comprises forming a second transparent adhesion layer between two of the inorganic barrier layers.
6. The method according to claim 1, wherein providing the hard coat of the sealing structure is selected from one of the group consisting of hardened coating, anti-reflective coating, and ¼ λ polarizer.
| 6465953 | October 15, 2002 | Duggal |
| 6570325 | May 27, 2003 | Graff et al. |
| 6573652 | June 3, 2003 | Graff et al. |
| 20020125822 | September 12, 2002 | Graff et al. |
Type: Grant
Filed: Jan 20, 2004
Date of Patent: Mar 29, 2005
Patent Publication Number: 20040152390
Assignees: Chi Mei Optolectronics Corporation , Kyocera Corporation (Kyoto)
Inventors: Chia-Tin Chung (Toufen Jen, Miaoli), Hao Jung Huang (Yuan-lin Chen Changhua Hsin), Chen Wei Huang (Tainan)
Primary Examiner: Joseph Williams
Attorney: Merchant & Gould P.C.
Application Number: 10/760,862
